package com.hmdp.service.impl;

import cn.hutool.core.bean.BeanUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.VoucherOrder;
import com.hmdp.mapper.VoucherOrderMapper;
import com.hmdp.service.ISeckillVoucherService;
import com.hmdp.service.IVoucherOrderService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisIdWorker;
import com.hmdp.utils.UserHolder;
import lombok.extern.slf4j.Slf4j;
import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.aop.framework.AopContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.connection.stream.*;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.PostConstruct;
import javax.annotation.Resource;
import java.time.Duration;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Slf4j
@Service
public class VoucherOrderServiceImpl extends ServiceImpl<VoucherOrderMapper, VoucherOrder> implements IVoucherOrderService {

    @Resource
    private ISeckillVoucherService seckillVoucherService;

    @Resource
    private RedisIdWorker redisIdWorker;

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private RedissonClient redissonClient;

    private static final DefaultRedisScript<Long> SECKILL_SCRIPT;

    static {
        SECKILL_SCRIPT = new DefaultRedisScript<>();
        SECKILL_SCRIPT.setLocation(new ClassPathResource("seckill.lua"));
        SECKILL_SCRIPT.setResultType(Long.class);
    }

    private static final ExecutorService SECKILL_ORDER_EXECUTOR = Executors.newSingleThreadExecutor();

    @PostConstruct
    private void init() {
        SECKILL_ORDER_EXECUTOR.submit(new VoucherOrderHandler());
    }

    private class VoucherOrderHandler implements Runnable {
        String queueName = "stream.orders";

        @Override
        public void run() {
            while (true) {
                try {
                    //1.获取消息队列中的订单信息
                    List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
                            Consumer.from("g1", "c1"),
                            StreamReadOptions.empty().count(1).block(Duration.ofSeconds(2)),
                            StreamOffset.create(queueName, ReadOffset.lastConsumed())
                    );
                    //2.判断消息获取是否成功
                    if (list == null || list.isEmpty()) {
                        //2.1.如果获取失败,说明没有消息, 继续下一次循环
                        continue;
                    }
                    //3.解析消息中的订单信息
                    MapRecord<String, Object, Object> record = list.get(0);
                    Map<Object, Object> values = record.getValue();
                    VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
                    //4.如果获取成功, 可以下单
                    handlerVoucherOrder(voucherOrder);
                    //5.ACK确认
                    stringRedisTemplate.opsForStream().acknowledge(queueName, "g1", record.getId());
                } catch (Exception e) {
                    log.error("处理订单异常", e);
                    handlePendingList();
                }
            }
        }

        private void handlePendingList() {
            while (true) {
                try {
                    //1.获取pending-list中的订单信息
                    List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
                            Consumer.from("g1", "c1"),
                            StreamReadOptions.empty().count(1),
                            StreamOffset.create(queueName, ReadOffset.from("0"))
                    );
                    //2.判断消息获取是否成功
                    if (list == null || list.isEmpty()) {
                        //2.1.如果获取失败,说明pending-list没有异常消息, 结束循环
                        break;
                    }
                    //3.解析消息中的订单信息
                    MapRecord<String, Object, Object> record = list.get(0);
                    Map<Object, Object> values = record.getValue();
                    VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
                    //4.如果获取成功, 可以下单
                    handlerVoucherOrder(voucherOrder);
                    //5.ACK确认
                    stringRedisTemplate.opsForStream().acknowledge(queueName, "g1", record.getId());
                } catch (Exception e) {
                    log.error("处理pending-list异常", e);
                    try {
                        Thread.sleep(20);
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
                    }
                }
            }
        }
    }

    /*private BlockingQueue<VoucherOrder> orderTask = new ArrayBlockingQueue<>(1024 * 1024);
    private class VoucherOrderHandler implements Runnable {

        @Override
        public void run() {
            while (true) {
                try {
                    //获取队列中的订单信息
                    VoucherOrder voucherOrder = orderTask.take();
                    //创建订单
                    handlerVoucherOrder(voucherOrder);
                } catch (Exception e) {
                    log.error("处理订单异常", e);
                }
            }
        }
    }*/

    private void handlerVoucherOrder(VoucherOrder voucherOrder) {
        Long userId = voucherOrder.getUserId();
        //创建锁对象
        RLock lock = redissonClient.getLock("lock:order:" + userId);

        //获取锁, 一个用户一把锁, 同一用户的并发请求会被串行化（只有一个线程能获取锁，其他线程需等待）。
        boolean isLock = lock.tryLock();
        if (!isLock) {
            log.error("不允许重复下单");
            return;
        }
        try {
            proxy.createVoucherOrder(voucherOrder);
        } finally {
            lock.unlock();
        }
    }

    private IVoucherOrderService proxy;

    @Override
    public Result seckillVoucher(Long voucherId) {
        //获取用户
        Long userId = UserHolder.getUser().getId();
        //获取订单id
        long orderId = redisIdWorker.nextId("order");
        //1.执行lua脚本, 操作Redis数据
        Long result = stringRedisTemplate.execute(
                SECKILL_SCRIPT,
                Collections.emptyList(),
                voucherId.toString(), userId.toString(), String.valueOf(orderId)
        );
        //2.判断结果是否为0
        result.intValue();
        if (result != 0) {
            //2.1不为0, 代表没有购买资格
            return Result.fail(result == 1 ? "库存不足" : "存在重复订单");
        }

        //获取代理对象(事务)
        proxy = (IVoucherOrderService) AopContext.currentProxy();
        //3.返回订单id, 先告诉用户已经下单完成,然后独立线程实现下单功能
        return Result.ok(orderId);
    }

   /* @Override
    public Result seckillVoucher(Long voucherId) {
        //获取用户
        Long userId = UserHolder.getUser().getId();
        //1.执行lua脚本, 操作Redis数据
        Long result = stringRedisTemplate.execute(
                SECKILL_SCRIPT,
                Collections.emptyList(),
                voucherId.toString(), userId.toString()
        );
        //2.判断结果是否为0
        result.intValue();
        if (result != 0) {
            //2.1不为0, 代表没有购买资格
            return Result.fail(result == 1 ? "库存不足" : "存在重复订单");
        }
        //2.2为0, 有购买资格, 把下单信息保存到阻塞队列
        VoucherOrder voucherOrder = new VoucherOrder();
        //2.3订单id
        long orderId = redisIdWorker.nextId("order");
        voucherOrder.setId(orderId);
        //2.4用户id
        userId = UserHolder.getUser().getId();
        voucherOrder.setUserId(userId);
        //2.5代金券id
        voucherOrder.setVoucherId(voucherId);
        //2.6.放入阻塞队列
        orderTask.add(voucherOrder);
        //获取代理对象(事务)
        proxy = (IVoucherOrderService) AopContext.currentProxy();
        //3.返回订单id, 先告诉用户已经下单完成,然后独立线程实现下单功能
        return Result.ok(orderId);
    }*/

    /*@Override
    public Result seckillVoucher(Long voucherId) {
        //1.查询优惠券
        SeckillVoucher seckillVoucher = seckillVoucherService.getById(voucherId);
        //2.判断秒杀是否开始
        if (seckillVoucher.getBeginTime().isAfter(LocalDateTime.now())) {
            return Result.fail("秒杀尚未开始");
        }
        //3.判断秒杀是否已经结束
        if (seckillVoucher.getEndTime().isBefore(LocalDateTime.now())) {
            return Result.fail("秒杀已经结束");
        }
        //4.判断库存是否充足
        if (seckillVoucher.getStock() < 1) {
            return Result.fail("库存不足");
        }
        Long userId = UserHolder.getUser().getId();
        //创建锁对象
        //SimpleRedisLock simpleRedisLock = new SimpleRedisLock("order:" + userId, stringRedisTemplate);
        RLock lock = redissonClient.getLock("lock:order:" + userId);

        *//*一人一单问题的本质是：
        多线程并发时，多个线程同时检查到 “用户未下单”，导致重复创建订单。
        需保证 “检查用户是否已下单” 和 “创建新订单” 的原子性。*//*
        //获取锁, 一个用户一把锁, 同一用户的并发请求会被串行化（只有一个线程能获取锁，其他线程需等待）。
        boolean isLock = lock.tryLock();
        if (!isLock) {
            return Result.fail("不允许重复下单");
        }
        try {
            //获取代理对象(事务)
            IVoucherOrderService proxy = (IVoucherOrderService) AopContext.currentProxy();
            return proxy.createVoucherOrder(voucherId);
        } finally {
            lock.unlock();
        }
    }*/

    @Transactional
    public void createVoucherOrder(VoucherOrder voucherOrder) {

        //5.一人一单
        //5.1查询订单
        Long userId = voucherOrder.getUserId();
        int count = query().eq("user_id", userId).eq("voucher_id", voucherOrder.getVoucherId()).count();
        //5.2判断是否存在
        if (count > 0) {
            log.error("用户已经购买过一次");
            return;
        }
        /*超卖问题的本质是：
        多线程并发抢购时，库存检查
        （判断库存 > 0）和库存扣减（stock-1）非原子操作，
        导致多个线程同时 “看到” 库存充足，最终库存被减为负数。*/
        /*该逻辑通过 SQL 层面的原子操作 实现库存扣减：
        整个update语句在数据库中是原子执行的(数据库会为该操作加行锁，避免并发冲突),
         只有当库存stock > 0时, 才会执行stock = stock - 1的扣减。
         即使多个线程同时发起请求，数据库也会保证只有满足条件的操作才能成功，
         最终库存不会出现负数，因此超卖问题被解决。*/
        //6.扣减库存, 原子性扣减库存（通过WHERE条件防止超卖）
        boolean success = seckillVoucherService.update()
                .setSql("stock = stock - 1")
                .eq("voucher_id", voucherOrder.getVoucherId())
                .gt("stock", 0)
                .update();
        if (!success) {
            log.error("库存不足");
            return;
        }

        //7.创建订单
        save(voucherOrder);
    }
}
